Recently, increasing social demands are directed to the protection of concrete structures and maintenance of the beauty thereof.
One of the weak points possessed by the contrete structures is believed to be the easy occurrence of cracks from various sources. To cope with the same, a number of elastic paints are placed on the market. However, most of elastic paints paints are based on a material having a low Tg value of less than room temperature and formulated into a low pigment-volume-concentration (PVC) and therefore indeed they are useful in giving coatings with excellent gloss and flexible properties which may well accommodate to the underlying cracks, but there are such problems that the coatings are generally deficient in moisture permeabilities and when applied with a top coat, there often result undesired blisters in the top coat and even peeling of the coat from the moisture condensation within the concrete.
In another technique of using sand textured coatings (Synthetic Resin Emulsion Type) (JISA-6909), since the material is formulated into more than the critical pigment volume concentration (CPVC), the resulting coating has innumerable fine voids and hence is excellent in moisture permeability and however, it is deficient in flexibility and cannot accommodate to the underlying cracks. Moreover, the waterproof properties of the coating against rain water is quite poor and thus, the coating cannot give enough protection for the concrete structures.
It is, therefore, an object of the invention to provide an aqueous coating composition capable of producing a coating with excellent gloss, flexibility and elongation which can well accommodate to the underlying cracks, as well as exhibiting improved moisture permeability and water resistance.